This invention relates generally to automated graphical input/output devices and more particularly to a precision digitizer in an automated artwork system.
The electronics industry has experienced a tremendous revolution through the innovations now permitted by integrated and printed circuits and transistorized systems. Many of the present electronic integrated and printed circuits are very small and even "miniature" as final products.
The production of these miniature electronic circuits requires several steps in transposing them from the engineered and designed circuit to the production equipment circuit.
Automated artwork systems, such as the system described in Norton, U.S. Pat. No. 3,601,590, have become increasingly important and useful in permitting the precise drafting required to perform the above stated transposing of miniature circuitry designs to and from various forms of two dimensional media. These systems generally feature interactive computer graphics facilities through which the modification, testing, and even redesign of input circuitry is made possible. Along with Norton the patent to Hart, et al, U.S. Pat. No. 3,534,396, is of interest, since it teaches an interactive computer graphic system for design analysis.
Drafting tables, such as those set out in the Norton patent, generally possess the characteristic that, in conjunction with a digital computer, each of the selected points along a subject contour is assigned a digital value in both the X and Y-axes of an arbitrary two dimensional coordinate system superimposed on the working surface of the drafting table. Automated drafting tables possessing the above stated characteristics are hereinafter referred to as "digitizers."
Prior digitizers suffer from several severe limitations affecting precision. It is to solving these limitations of prior digitizers that the invention is directed.
In particular, the usual construction for prior digitizers employs a cantilever arrangement, such as shown in FIG. 1 of the Norton Patent, wherein a Y-axis arm, including moveable cursor, is mounted at right angles to and upon a single X-axis rail. The cantilevered construction as shown is mechanically unstable in that the digitizer lacks rigidity. As a result, input accuracy may be adversely affected by small factors such as the weight of an operator's hand upon the cursor, from slew, etc. In addition, the cantilevered structure is not structurally rugged and requires frequent readjustment and maintenance in order to insure the right angle relationship between the Y-axis arm and the X-rail.
Further problems inherent in prior devices include poor mechanical force control. By way of illustration, the electromechanical forces applied in response to computer generated signals for the cursor and/or Y-axis arm to move in a given direction are often retarded by friction or free arm instability. Thus, the precision of digitized input data and the precision of computer generated output are further affected.
Further yet, prior means for inputing data into the digitizer have been subject to human error factors resulting from visual vantage point parallex. Briefly, the physical position from which the operator views a target location for input may affect the digital value assigned to the target since the actual target location may appear at different locations depending on where the operator is standing. This problem not only causes imprecise input but tends to decrease reliability and make repeatability of digitizing and drafting tasks virtually impossible. This is especially true when the vantage point parallex problem is combined with the other problems set out hereinbefore.
It is therefore an object of this invention to provide precise digitizer apparatus not prone to be affected by such problems as the aforementioned slew, force on the cursor, and human error that significantly affect prior digitizer apparatus.
It is a further object to provide a precision digitizer apparatus requiring only infrequent maintenance as compared with the less rugged units known in the prior art.
It is still a further object to provide precision digitizer apparatus can repeat digitizing and drafting tasks in a highly reliable and predictable manner.